1. Technical Field
This invention relates generally to electronic circuits, and more particularly to a semiconductor circuit achieving greater gain with fewer components for amplifying radio frequency (RF) signals at frequencies over 300 megahertz (MHz).
2. Description of Related Art
A semiconductor circuit designer creating an RF power amplifier circuit seeks high performance in a small package. Recent developments of GaAlAs/GaAs heterojunction bipolar transistors (HBTs) contribute by providing semiconductor devices having better high frequency performance. But existing RF amplifier circuits frustrate the effort by requiring too many supporting components.
Consider the task of designing a 2-stage, 1.4 watt, RF amplifier for a cellular telephone operating in the 800-MHz band. Known design techniques couple an external dc-bias circuit to each stage of the RF circuit through an isolating RF choke. In addition, they use reactive matching for interstage RF coupling as well as input and output RF coupling. The problem is that all the components required to do that make the RF amplifier large in size (e.g., 1.6 cm by 1.0 cm) and difficult to implement in a small integrated circuit (IC) package. Thus, designers need an RF amplifier circuit alleviating that concern.